Abstract A predictable means of regenerating bone in the craniofacial area is critical. Typical surgical therapies to reconstruct bone include the use of combined osteoconductive and osteoinductive materials. However, there is wide variation in results of currently implemented bone regeneration therapies due to a combination of factors such as variable remodeling rates of the scaffold, bioavailability of growth factors, triggering of unwanted side effects such as inflammation, fibrous encapsulation and even ectopic ossification. One of the most potent inductive biologic is bone morphogenetic protein, BMP, but it is a high cost therapy making its use prohibitive for a large portion of the population specifically for dental care. We have in vitro preliminary data showing that the natural flavonoid compound extracted from citrus fruits, hesperidin (HE), up-regulates expression of key osteoblast differentiation markers, enhances the quality of the collagen matrix and mineral-to-matrix ratio in vitro, and prevents osteoclast formation. Further, we have in vivo data showing that HE promotes bone formation in a critical-sized craniofacial bone defect (CSCBD) and the growth of bone forming cells is stimulated in an HE-based scaffold. Previous reports have shown that this compound can prevent loss of bone density in ovariectomized rats. Our central hypothesis is that HE increases and accelerates the rate of bone formation by favoring osteoblast vs. osteoclast function, promoting wound healing and positively affecting quality of extracellular matrix formation in a CSCBD as compared to a well-known bone promoting factor such as BMP2. This proposal will utilize a CSCBD in the mandible of rats which will be treated with an HE-collagen scaffold while addressing the following specific aims: 1) We will characterize the bone healing profile of HE- treated defects in early post-surgical stages of the mandible osteotomy model (3 and 7 days) by analyzing wound healing, osteogenic and osteoclastic markers as well as associated signaling pathways; 2) We will characterize bone vascularity and kinetics of bone formation during early and mid-healing stages (14 and 30 days) of the osteotomy sites treated with HE by functionalized micro-computed tomography (CT) and fluorochrome-aided histological studies; 3) We will characterize the quality of the fully regenerated bone in response to HE (matured up to 60 days) as compared to exogenous BMP2 by imaging, biomechanics and histology. Preliminary data is very promising on the effect of HE on bone regeneration and potential mechanisms. The results of our studies could have a major impact on regenerative medicine/dentistry by means of introducing a simple, cost-effective, alternative and predictable bone inducing therapy for bone defects. This proposal will contribute to the fulfillment of NIDCR's mission of improving craniofacial health as it will lead to the discovery and characterization of the effects of a novel agent for treatment of large bone defects that has predictable anabolic properties.